Intelligent lighting for the 21st century | Part 3

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Learn more about two great innovative camera features

GigE Vision and GenICam

Gigabit-Ethernet for Machine Vision or, in short, GigE Vision: According to
many experts, the new interface standard and the closely associated generic
software interface GenICam (Generic Interface for Cameras) will give new
impetus to the industrial image processing sector in the near future: The
image processing industry finds itself at a crucial technological watershed!

How does a camera image actually arrive at the PC that evaluates it? The
question is not as simple as it seems and in the world of industrial image
processing there are now a whole range of possible answers, which are the
subject of a lively debate. You will hear a plethora of terms such as
"CameraLink", "IEEE-1394" - also known as "FireWire" - encompassing both FireWire A and B versions, as well as "USB", "USB 2", "Gigabit Ethernet" or "10 Gigabit Ethernet". And as if these standard transmission methods, (most of which come from the consumer PC world), were not enough, there are also a large number of other, proprietary methods. This bewildering range of available options does not make it easy for users to select the most suitable components at the best prices when planning a new image processing solution.

Gigabit Ethernet for Machine Vision ("GigE Vision" for short) is a
standard that has entered the fray and could potentially become the preferred
interface for vision applications. Firstly, the standard defines a uniform
protocol based on UDP/IP, which will allow GigE Vision compatible image
processing products to communicate with a host. Secondly, GenICam, which is referenced by the standard, is intended to create a common software interface that allows devices to communicate their functions to any compatible software using a standardized XML format file. The combination of a uniform protocol
plus an XML definition makes it possible to use hardware-independent software
from any manufacturer with any GigE enabled device, making it easier to
exchange image processing hardware if required.

Huge benefits for the users

This new technology offers users a whole range of benefits. The key issue has
already been mentioned: making it easier to exchange hardware, should the need
arise. This in turn promises shorter design cycles, lower development costs
and as a result, greater opportunities in the market.

In addition to this, and to an even greater degree than both
FireWire/IEEE-1394 and USB 2.0, GigE Vision offers the advantages of an
industrial standard which is constantly being developed and will also be
available as 10 GigE in the future. The use of mass market Ethernet technology
as a basis of GigE Vision means that image processing will benefit from less
expensive components. Add to this the wide selection of standard industrial
connectors, cables and components such as routers and switches that are
available in IPXX variants and GigE Vision’s suitability for deployment in
tough industrial environments becomes compelling.

Additionally, it should be remembered that for the first time, Gigabit
Ethernet, (unlike its predecessor FastEthernet), will deliver sufficient
bandwidth over "normal" network connections to meet the high bandwidth demands
found in many image processing applications. At a planned data rate of
approximately 100MByte/s, GigE Vision caters for the vast majority of common
image processing applications.

Other user benefits include the ability to run any number of devices on a
single host, the potential for remote maintenance, and simpler implementation
of distributed computing.

Also, thanks to the widespread use of this technology, Gigabit Ethernet offers
considerably longer and very inexpensive cable lengths, that are available in
grades that are suitable for chain cable carriers and robots,. According to
the specification, distances of up to 100m are possible, which could
previously only be achieved using a range of other technologies with a
considerable amount of effort, for instance, using repeaters with CameraLink
cables or hubs with IEEE-1394 or even switching to a completely different
medium such as fibre-optic or coaxial cabling. If even greater distances are
required, fibre optic cables can also be used with Gigabit Ethernet. But even
that is not the whole story with respect to data transport: Initially, the
underlying transport medium is of no significance in the GigE Vision and
protocol definition. Thus, for instance, the way is open to deploying 10 Gbit
Ethernet in the future when this technology becomes affordable and/or when it
becomes possible to use 10 GigE Vision over copper wire.

All these advantages make a strong case for the claim that GigE Vision will
soon be able to play a meaningful, powerful role in industrial image
processing. As for the major manufacturers, the support is already there. The
GigE Vision standardization committee is assigned to the AIA (Automated
Imaging Association) and is thus sponsored by many of the leading image processing manufacturers across the world. This includes companies such as
Basler Vision Technologies, Teledyne DALSA, JAI, Matrox, National Instruments, PhotonFocus, Pleora Technologies and of course, STEMMER IMAGING.

A completely new approach to software

Past experience means that it should come as no surprise that the industry is
trying to define GigE Vision as a separate standard, after all, the purpose of
a standard is to facilitate the integration of hardware components or
guarantee that components can be exchanged as well as to minimize the costs
and time involved in integration. The development of CameraLink was a first
step in this direction and defined the hardware interface between the camera
and the host. However, the software was not sufficiently catered for, since
CameraLink only defined serial communication, completely ignoring the
functionality of the camera. The approach adopted in IEEE-1394/FireWire was
far more extensive, as it laid down a more or less fixed register layout for
the functionality of the camera. But it was precisely this relatively
inflexible structure to the register layout which proved to be problematic.
The fatal flaw was the fact that there was no reference implementation, which
led to the current situation where every manufacturer of FireWire products
supplies their own SDK. For the customer, this means that it is no longer a
simple matter to exchange IEEE-1394 hardware products.

GigE Vision and GenICam have adopted a different approach which is not
intended to dictate the functionality of the cameras. Instead, the standard is
designed to provide a flexible description of the camera features which can
then be used by a generic software product. (See the GenICam diagram)

Principle of GenICam: The aim of GenICam is to provide complete plug & play functionality.

And how does that work in detail?

An XML file is used to describe the cameras features and functions, which
ultimately describes the register map. The manufacturers use this file to
store detailed information about their product in XML format (described in the
standard) and this explains how and where these can be addressed. Thus, for
instance, a register controlling the gain of a camera can be located anywhere
in the register map for that camera. Using the XML file, the software is then
able to adjust this gain.

Being able to use any generic software product, it is simple matter to address
any function of a camera (or other device) or to access parameters. GenICam is
therefore responsible for defining the layout of the XML file and for making
available a reference implementation which is able to control the camera and
capture data from it. In subsequent versions, GenICam will also abstract the
communication layer to the camera, allowing it to be used for FireWire or
CameraLink cameras.

To achieve this, the mechanisms required for communicating with the camera
will be abstracted and encapsulated in a special communication layer called
the ‘Transport Layer’. Replacing this layer will then make it possible to
communicate not only with GigE Vision components but also with IEEE-1394 or
other register-based devices. In a further step, the functionality will then
be extended to support not only pure register access, but also the exchange of
‘string tokens’ which would then allow GenICam to be used for CameraLink
cameras also.

GigE Vision & GenICam: Block diagram with transport layer

The way to a standard

From the very start, STEMMER IMAGING has played a major role in defining both of these standards. The Puchheim-​based company has already made effective use of this advantage by channelling this knowledge into the current version of its image processing library, Common Vision Blox (CVB) which was one of the first image processing software packages to comply with the GigE Vision and GenICam specifications, making it is ideally equipped to take advantage of this new technology.

Conclusion

GigE Vision and GenICam offer exciting new image processing interfaces. Never before has the entire vision industry been in agreement to such an extent as they have been when defining the GenICam standard. Both technologies have the potential to open up new markets and to further extend the horizons of image processing.

The Author

Rupert Stelz is member of the GigE Vision Technical Committee and Senior Development Engineer at STEMMER IMAGING GmbH, Puchheim.